Hi; that happened to me time ago, since our first ADMN installation, when you create a computer, or install from a msi file, the computer object was created in the main group "Computer Catalog", by default the policy is to block the Avast icon in task bar (right click on computer catalog, properties, policies, local scanners, on-access user interface), so we created some subgroups, broke the policy inherit, then we were able to open the program from the avast icon, (we let this option enable only for our servers, not for users) any way, you must be able to open Avast from "Start", "All programs", "Avast Antivirus (managed)", "Avast! Antivirus"
I hope it could help you!
Best Regards!
Sergio Ariza.